Method and means for studying sound



Aug. 11, 1936. F M, ROBE 2,050,380

METHOD AND MEANS FOR STUDYING SOUND Filed NOV. 16, 1934 Fr ank Morse R0 b'b' ATTO R N EY Patented Aug. 11, 1936 UNITED STATES METHOD AND MEANS non s'runmo SOUND Frank Morse Robb, Bellevllle, Ontario, Canada Application November 16, 1934, Serial No. 753,247

5 Claims.

This invention relates to methods and means for for studying sound. and is a companion invention to the one covered by applicants patent number 1,964,929, issued July 3, 1934, entitled Methods 5 and apparatus for studying sound.

' An object of the invention is to .provide an electricalinstrument in which an opposing current is generated in the circuit which entirely neutralizes and wipes out what is known variously as the slot 10 tone, scanning tone, disc tone or inherent tone, thereby maintaining the output voltage line at zero until a waveform mask is placed before the scanning disc, in which case only the natural tone of the wave form will be heard.

15 Another object of the invention is to provide a method and means for obtaining a musical tone from a waveform mask without hearing the scanning tone along with it, said method and means being accomplished not by a photo-electric cir- 2 cuit but by electro-magnetic means, which effect this elimination of the scanning tone while still permitting the full and natural sound of the waveform being scanned. All these and other objects as suggested here 25 below are attained by the methods and means now to be described, and illustrated in the accompanying drawing, in which- Figure 1 shows the face of a scanning wheel with three waveform tabs and the pickup and field coils in diiferent positions.

' Fig. 2 shows a side elevational view of the scanning-wheel of Fig. l, positioned in operating rela- 'tion between the neutralizing pickup and the tone 35 Fig. 3'shows a diametral cross sectional view of a drum type of scanner (as distinguished from the disc type of the previous views) with the neutralizing and the tone pickup coils on the South and North Poles of a single magnet.

Fig. 4 is a plan view of a sheet iron tab such as is used to cut the waveform in.

Fig. 5 shows the tab of Fig. 4 with a wave form cut therein, and

Fig. 6 shows the belt type of scanner with 45 three tone pickups and the neutralizing pickup.

Like numerals refer to like parts throughout the several views.

In applicant's previous patent, above. mentioned, is shown the construction of a photo-electric instrument which, when in operation, produces no sound until the shadow of a wave form falls upon its screen or aperture; and which isso designed that it generates sound waves in theair which in their form are a faithful reproduction 5 of. the waveform shadow which has been cast upon the aperture of the instrument. In other words, this photo-electric instrument has no inherent tone of its own, but will give out only the quality of sound represented by the contour of the shadow cast on its aperture. which is of utmost 5 importance inthe precise study of sound waves and musical qualities. 4 1

Now while this photo-electric apparatus is very successful, it has seemed advantageous to make an instrument still more simple in design which, can be used for the same purposes. Therefore applicant has invented a new apparatus using the principle of the generation of electric current in coils through which is passing a magnetic flux. In this new apparatus an opposing current is generated in the circuit which entirely neutralizes and wipes out what is known variously as the slot tone, scanning tone, disc tone or inherent tone, thereby maintaining the output voltage line at zero until a waveform mask is placed before the scanning disc, in which case only the natural tone of the waveform will be heard.

Until applicant's invention of the photo-electric apparatus as disclosed in Patent 1,964,929 above hnentioned, there was no known means of obtaininga musical tone from a waveform mask without hearing the scanning tone along with it.

After the above invention there was still no known means of accomplishing this particular re= sult in any circuit other than a photo-electric one until this invention of the electro-magnetic design as disclosed here, which effects this same elimination of the scanning tone while still permitting the full and natural sound of the waveform being scanned.

The scanning wheel of Fig. 1 consists of a plurality of equi-spaced iron ribs I0 set in a -brass or bakelite disc 1 I. v

On scanning wheel l0-H are shown three waveform tabs I2, 13, II, the pickup and field coils being represented by dotted lines IS. The arrow shows the direction of rotation. Tabs l2 and I3 are in normal position, and it will be noted that the shape of these tabs, apart from the waveform, is such that one scanning rib will cross over 5 :the narrow pickup coils. By turning the knurled thumb nut I! the pickup will be advanced or retreated through the threaded support 23, and the waveform tab thus moved closer to or farther from the scanner. A twist of the little handle on the-magnet core, or 2|, will turn the waveform tab i2 (for example) around on its axis. Members I3 and 2| are of soft iron, while support 20 is of brass or other non-magnetic material.

In this'view the south pole is at "A and the north pole opposite at I3A. Member 2| connects with and turns the rotatable magnet core 22. In this view washers are shown at 23 and knurled nut i9 connects with and turns hollow magnet 24 containing an adjusting thread adapted to be screwed through companion threads in support 20.

In Fig. 3 is shown a drum type of scanning wheel 25 driven by axle 26. said member 25 being made of iron and containing slots 21. The field coil is shown at 28, the pickup coils at 29 and 30, the waveform tab at 2, and the north and south poles respectively designated by N" and S. In this view the neutralizing and tone pickup coils are shown on the south and north poles of a single magnet. The waveform tab 2 is shown on the north pole.

In Fig. 4 the sheet iron tab to be used to cut the waveform in is shown at 3| and the waveform out in such tub is shown in Fig. 5 at 32.

In Fig. 6 the speaker is shown at 33, the amplifier at 34, a variable resistance at 35, a six volt current supply at 36, and the belt type of scanner comprises two pulleys 31-31 adapted to be rotated in direction of the arrows to in turn move the belt scanner 38. There is also shown three tone pickups 33, and 4|, and the neutralizing pickup 42. A waveform tab I2 is shown on the pole of pickup 4|.

The circuit in Fig. 6 is shown for several tone pickups with a single neutralizing pickup, as described above, this neutralizing pickup having a multiple wind field coil. When a contact is made by closing any one of switches 43, a current is sent into a field coil on its corresponding tone pickups 33, 40, 4| and also into one of the windings on the field of the pickup 42. Thus the neutralizing pickup is always energized in proper proportion for one, two or more tone pickups. The pickup coils are here shown permanently in circuit. The variable resistance 35 permits the neutralizing current from the pickup 42 to be cut down in case it is a little too strong. 01 course the N's in this figure designate north pole and S designates south pole.

Thus it will be seen that in the present invention the obtaining of natural quality of sound from a waveform member without any accompanying scanning tone is effected by means of opposing poles of magnets having pickup coils on them, the poles being evenly shaped and so placed in relation to the scanning slots or ribs v that the positive current generated in one pickup coil at any given instant will be exactly equal to the negative current generated in the other pickup coil. The two currents will thus neutralize each other, and the output of the circuit will be zero, until an iron or steel waveform member be placed on the pole of one magnet, when the balance will be upset and a current will appear in the circuit; and the electrical waveform of this current will have the same profile as the waveform on the iron member, and will not be distorted by any scanning tone as would be the .scanning tone of several other pickups of opcase if the neutralizing effect as set forth here were not employed.

It is possible to use one neutralizing pickup of greater magnetic strength to balance out the passing over the iron waveform set up a mag- 15 netic fiux in the magnet, the character of which depends on the shape of the waveform on the tab. This flux sets up an electric current in the pickup coil which must have that same waveform. 20

As the waveform tabs are so shaped in relation to the ribs of the scanner that one rib is just passing oil the tab as the next rib is coming on, the generated current will be continuous and earphones-or other sounding apparatus connected 25 in the circuit will give out a sustained tone, the musical quality of which will be that of the waveform which has been cut on the tab. For instance, if the waveform of a baritone human voice has been cut on the tab, the earphones will give out a baritone voice tone, and that tone will be natural and free from any additional superimposed tone from the scanner itself.

This is of vital importance. Without any balancing out, a scanning wheel gives out a "reed pipe" organ tone, and when one wishes to investigate a particular waveform, say that of a cello, one does not wish to hear it accompanied and drowned out by this reed-like organ tone. Hence the value of this invention, the proof of which 40 scanner itself. 45

It is sometimes interesting, however, to distort the waveform deliberately by turning the waveform profile on the tab to an angle with the scanning ribs. This results in an exaggeration of some of the partials of the tone and a suppression of others and produces an entirely new tone. To accomplish this the pickups are made with poles which can be revolved and thus be made to twist the waveform tabs on them to different positions.

The invention includes also the use of what is believed to be an entirely new method of sounding tones, the advantages of which are that all pickup coils remain continuously in the circuit, 60

making the designing of a circuit for a multiplicity of pickups a simple matter; and the tones sound and cease without the usual annoying click caused by the make and break of contacts; also the attack is pleasant, the tones coming on with 65 a slight scoop as with all musical instruments.

' This new method, then, consists of the use of field coils on the pickup magnets in addition to the pickup cofls, contact to sound the tones being made to the field coils which thus being en- 7( of iron is used for the waveiorm tabs and for the ribs on the scanning wheel.

With this arrangement, although several pickup coils are in the circuit, those pickups which have had waveform tabs placed at their poles still will not generate any tone current until the proper contact 'keys are pressed to energize their field coils. In other words, there can be no magnetic flux at the pickup poles unless there is current in the field coils, and when there is no flux there will be no tone current generated in the pickup coils.

There has heretofore been proposed the use of tone wheels in combination with varied shapes of pole pieces for the pickup magnets. But such pole pieces are intended merely to alter slightly the characteristics of the wave form which is on the tone wheel. But this applicant is the first to use a scanning disc which itself has no wave-form other than its slotting, and which is intended to scan a natural wave form on a pole piece in exact repetition and with such exact dimensions of thewave form in relation to the distance between the slots in the scanning disc or ribs of iron, as the case may be.

In the prior invention referred to above, there is simply a tone wheel with a varied pole piece, the

combination being used to reproduce whatever tone has been recorded or cut on the disc, and to permit slight variations or exaggerations of this tone by altering the shape of the pole piece.

Having now described the invention, what is claimed as new and for which Letters Patent of the United States is desired, is:

1. The combination with a scanning member free of any wave form but having ribs or scanners 5 of magnetic material, of pickups of opposing magnetic poles so shaped and placed that the currents generated in their pickup coils oppose and neutralize each other in the circuit to result in a zero output voltage.

2. The invention as in claim 1, including the use of waveform tabs of such shape that one scanning rib will be just starting to pass over the one end of the tab as another rib is passing off the other end, to thus produce a continuous generation of the electrical waveform without gap or overlap.

3. The invention as in claim 1, including the use of revolving pickup poles so arranged that the waveform tabs may be turned to different positions in regard to the scanning ribs, to thereby produce diflerent distortions of tone.

4. The invention as in claim 1, including the use of pickup coils permanently in circuit, with their magnets and the waveform tabs and scanning ribs 01' a kind of metal which drops its magnetism instantly, and including field coils on the pickups connected to contact keys which feed energizing current when contact is made. I

5. In an electro-magnetic circuit, means of obtaining a musical tone from a waveform mask without hearing the scanning tone along with it, said means including a scanning 'disc free of any wave form and means associated therewith for generating an opposing current in the circuit to entirely neutralize and wipe out what is variously known as the scanning tone, slot tone. disc tone or inherent tone.

FRANK MORSE ROBB. 

